Well, in order for the Earth to suddenly start spinning in a different direction, it would need to stop to change the direction of spin. That would be pretty catastrophic since the Earth is spinning at 1000 mph / 1600 km/h (at the equator) and since we're standing on the Earth we're also moving at 1000 mph (again, at the equator). So imagine being in a car crash where the car suddenly stops except the car is moving faster than the speed of sound... it wouldn't be pretty.

You'd have to be pretty close to either of the poles to survive the stop, even at 80 degrees north/south the rotational speed is still 180 mph / 280 km/h.

EDIT: Forgot to mention that everything, not just humans, currently sitting on top of the Earth would be affected by a sudden stop. Trees, buildings, bridges, ships, oceans, even the atmosphere itself would be sent flying along with us. So yeah, don't expect to survive that.

Setting aside the moment of the shift (where everything would go flying from the sudden change in movement) - yes, changes would absolutely happen. A reversal - so that the rotation of the earth is from east to west - would actually affect more than you might think. If you look at southern South America, you can see the effect that the direction of prevailing winds has. Many deserts would become lush, and many jungles would become deserts.

Massive climate changes. Oceans currents and prevailing winds are governed by the spin. We'd get whole new deserts and forest regions and that would lead to mass extinction of plants and animals (and humans) since few species would be able to adapt to the sudden change of climate.

That would mean the Earth would be slowing down for millions of years to change direction. Days and nights would become longer and longer as the Earth slowed until one side of the Earth would be in near permanent sunlight and the other in complete darkness.

All plant life on the side in darkness would die out without sunlight for photosynthesis. With plants gone, plant eating animals would be wiped out and predators would follow soon after.

On the side in the Sun things wouldn't be much better as the sunlight would scorch and burn large areas of land, turning it into desert.

Life might be able to survive in small pockets on the border regions between night and day or in the deep sea protected from the Sun. But most life would die out and the Earth would, at the very least, need millions of years to recover once the spin in the opposite direction had gotten up to speed and a proper day night cycle reestablished.

I doubt humans would survive such an event, food would be scarce and oxygen production severely diminished with much of the plant life wiped out.

No, we would almost all be very nearly instantly killed if it occurred suddenly. If the rotation suddenly reversed, someone standing on the top of a mountain may be flung into the air and thus achieve a temporary vantage point from which to observe air ripping across the surface at roughly 2000 miles per hour, scouring the surface clean of anything not completely destroyed by the initial jolt. However, it would probably generate enough heat to become rapidly lethal.

Someone on the ocean may briefly get to ride a wave across a continent as the major landforms suddenly stop traveling with the ocean and instead reverse, plunging into the water in the most tumultuous rapids every produced, but the impact might be strong enough to obliterate anything on the surface. If the earth simply stopped, the sea would crash into it at 1000 miles per hour. Reversing, it's going to hit at roughly 2000 miles per hour. It'd be quite an impact.